This invention relates to devices for imparting continuous passive motion to a limb or digit, and more particularly to portable units for exercising joints of the hand, fingers and wrist.
It has been standard medical procedure for many years to use exercise routines to restore mobility of limbs and joints after injury or immobilization, so as to overcome muscle degeneration and internal adhesions. It has more recently been recognized that "continuous passive motion" (CPM) exercises are desirable following traumatic incidents or operations. They can be initiated quickly, and by providing motion of a limb or digit, establish or maintain freedom of motion well before the musculature can function autonomously. Continuous passive motion devices have accordingly been developed in a number of forms, as evidenced by U.S. Pat. Nos. 4,487,199, 4,537,083 and 4,716,889. The devices depicted therein are not indicative of the state of the art, however, since units with additional features have been sold for some time by Kinetec of France, and by Toronto Medical Inc. of Yellow Springs, Ohio. Even such units, however, provide only a limited ability to supply motion effects and controls as dictated by a therapist for a given individual. The French system is a relatively cumbersome unit which must be operated from a power main. The Toronto Medical Inc. product is a portable battery operated device for exercising the fingers. A light weight battery operated CPM is very useful because of the frequency of occurrence of hand injuries, provided that a variety of manipulative CPM functions can be performed. It may be desirable, for example, to reciprocate the fingers from an intermediate partially flexed position to fully extended position, to reciprocate the fingers between partially flexed and fully clenched positions, or to use any other combination of finger or digit motions. It is evident that the same unit with minor adjustments or replacements should function for all desired finger positions. In addition, the unit should also be adaptable for imparting continuous passive motion to the thumb, and alternatively to the wrist. The unit should also permit a therapist to exercise only certain fingers and to introduce digit blocking or to exercise only particular fingers or joints.
In addition, ease of attachment, setting and adjustment are of significant importance inasmuch as the patient must ordinarily operate the machine after selection of specific exercises by the therapist. Settings should be easily controllable by the patient or therapist, and the design should enable full motion of each finger, if desired, despite variations in hand size, finger length, and finger alignment. Not only the extent of travel but also the rate of travel should be controllable.
As evidenced by the above referenced patents, it has been thought desirable to automatically reverse the reciprocating motion upon encountering a predetermined load. This type of control is very difficult to achieve, particularly because finger loadings are not uniform. Moreover with a properly adjusted device there is no need for such a function. In fact, it is often desirable to introduce stretching forces, in order to overcome adhesions and inhibiting forces, and to do so independently on each finger. Sometimes the fingers should be maintained in a given position for a dwell period at the end of a motion, providing a traction effect that enhances the healing process. Nonetheless, the action as far as each finger is concerned should be force limiting and a range of adjustment should cover the range of travel down to as little as one-quarter inch.
Superimposed on all of these requirements, a portable CPM unit should not only be light in weight but efficient in operation so that it can operate for a long interval on battery power. Moreover, not only the range of travel but the speed of reciprocation should be adjustable. Various useful features, such as counting the number of cycles, automatic resetting and manual or automatic operation, should also be provided.